add reansform option 'resize-pad' to dataset_tool.py that first scale…

…s an image into bounds then pads the image to the specified size

dataset_tool.py

@@ -250,16 +250,55 @@ def center_crop_wide(width, height, img):
         canvas[(width - height) // 2 : (width + height) // 2, :] = img
         return canvas
 
+    def _to_rgb(img):
+        # add channel dim
+        if img.ndim == 2:
+            img = img[:, :, None]
+        assert img.ndim == 3, f'input image has incorrect number of dimensions, required 2 (H, W) or 3 (H, W, C), got: {img.shape}'
+        # to RGB
+        if img.shape[-1] == 1:
+            img = img.repeat(3, axis=-1)
+        elif img.shape[-1] == 4:
+            img = img[:, :, :3]
+        assert img.shape[-1] == 3, f'input image must have 1 or 3 channels, got: {img.shape}'
+        return img
+
+    def resize_pad(width, height, img):
+        img = _to_rgb(img)
+        # exit early
+        img_h, img_w = img.shape[:2]
+        if width == img_w and height == img_h:
+            return img
+        # get scale size, avoiding precision errors
+        scale_ratio = max(img_h / height, img_w / width)
+        scale_h = int(round(img_h / scale_ratio, 5))
+        scale_w = int(round(img_w / scale_ratio, 5))
+        assert scale_h <= height and scale_w <= width, f'scaled shape {scale_w}x{scale_h} is not smaller than or equal to the required shape: {width}x{height} this is a bug:'
+        # scale image
+        img = scale(scale_w, scale_h, img)
+        # pad the image if needed
+        pad_h, pad_w = height - scale_h, width - scale_w
+        if pad_h != 0 or pad_w != 0:
+            pad_dims = [[np.floor(pad_h/2), np.ceil(pad_h/2)], [np.floor(pad_w/2), np.ceil(pad_w/2)], [0, 0]]  # (H,W,C)
+            img = np.pad(img, np.array(pad_dims).astype('int'))
+        # check the shape
+        assert img.shape[0] == height and img.shape[1] == width, f'output shape {img.shape[1]}x{img.shape[0]} does not match required shape: {width}x{height} this is a bug!'
+        return img
+
     if transform is None:
         return functools.partial(scale, output_width, output_height)
     if transform == 'center-crop':
         if (output_width is None) or (output_height is None):
-            error ('must specify --resolution=WxH when using ' + transform + 'transform')
+            error ('must specify --resolution=WxH when using ' + transform + ' transform')
         return functools.partial(center_crop, output_width, output_height)
     if transform == 'center-crop-wide':
         if (output_width is None) or (output_height is None):
             error ('must specify --resolution=WxH when using ' + transform + ' transform')
         return functools.partial(center_crop_wide, output_width, output_height)
+    if transform == 'resize-pad':
+        if (output_width is None) or (output_height is None):
+            error ('must specify --resolution=WxH when using ' + transform + ' transform')
+        return functools.partial(resize_pad, output_width, output_height)
     assert False, 'unknown transform'
 
 #----------------------------------------------------------------------------
@@ -321,7 +360,7 @@ def folder_write_bytes(fname: str, data: Union[bytes, str]):
 @click.option('--source', help='Directory or archive name for input dataset', required=True, metavar='PATH')
 @click.option('--dest', help='Output directory or archive name for output dataset', required=True, metavar='PATH')
 @click.option('--max-images', help='Output only up to `max-images` images', type=int, default=None)
-@click.option('--transform', help='Input crop/resize mode', type=click.Choice(['center-crop', 'center-crop-wide']))
+@click.option('--transform', help='Input crop/resize mode', type=click.Choice(['center-crop', 'center-crop-wide', 'resize-pad']))
 @click.option('--resolution', help='Output resolution (e.g., \'512x512\')', metavar='WxH', type=parse_tuple)
 def convert_dataset(
     ctx: click.Context,